A process of producing a stretch sheet is known, in which a sheet material having elastic stretchability and a substantially inelastic sheet material are joined together in parts and then stretched. For example, EP 0556749A1 discloses a process of producing a stretch composite sheet, comprising joining an elastic sheet in its relaxed state and a base sheet having extensibility equal to that of the elastic sheet but non-recoverable continuously in the longitudinal direction (MD) and discontinuously in the width direction (CD) to make an elastic composite sheet, stretching the elastic composite sheet to cause the base sheet to be deformed permanently within a limit that does not cause the base sheet to cut or break, and releasing the composite sheet from the stretched state.
However, conventional processes of producing a stretch sheet as described above are disadvantageous in that the two sheet materials joined in parts tend to separate on stretching, depending on the degree of stretching. It would follow that the resulting stretch sheet has insufficient tensile strength or easily fuzzes or breaks to have a poor hand or appearance. Such inconvenience could be averted by, for example, lowering the stretch ratio, which makes it difficult to produce a highly stretchable sheet.